The present invention relates to a method of cleaning air in a compressed air system. It also relates to a use of this method as well as a device for carrying out the method.
A compressor delivers air to the compressed air system. This air is conventionally passed through an air dryer, where the air is dried by means of desiccant or molecular sieve.
However, the air coming from the compressor is a mixture of gas, solid particles and liquid particles. The mixture is called an aerosol. The size of the particles can typically be in the range of 0.001-15 xcexcm. The particles can form larger clods, so called agglomerates. Larger liquid particles can be mechanically trapped.
Some of the particles are already in the air fed into the compressor, whereas others are added in the compressor, especially if it is of the piston type (where lubricating oil will be added to the air).
The molecular sieve has the purpose to take up moisture and is cyclically regenerated for removing this moisture. It is, however, well known that all other matter introduced therein by the air is detrimental for its function, so that it has to be replaced at intervals. Also, the air leaving the molecular sieve will contain matter that can cause problems and damages in the compressed air system, and this problem is increased with the ageing of the molecular sieve.
The main object of the invention is accordingly to remove the above stated deficiencies with presently used air drying systems and to obtain a cleaning rather than a mere drying of the air delivered to the compressed air system.
This is according to the invention attained by consecutively passing the air through at least one of the following media in addition to a molecular sieve:
a pre-filter,
silica gel, and
a fine filter,
wherein the pre-filter and the silica gel are upstream from the molecular sieve and the fine filter downstream thereof.
Preferably, the air is consecutively passed through the pre-filter, the silica gel, the molecular sieve, and the fine filter.
The method according to the invention is preferably to be used in compressed air systems for automotive application, especially for heavy road vehicles, but other uses are equally possible.
A conventional cartridge for an air dryer has a cylindrical housing provided with a cylindrical wall dividing the housing in an annular outer compartment and a cylindrical central compartment. In this cartridge the pre-filter and the silica gel can be arranged in the outer compartment and the molecular sieve and the fine filter in the central compartment.